The invention relates to casters in general, more particularly to improvements in casters which are provided with brakes for controlled frictional engagement with their wheels.
Commonly owned German Pat. No. 27 21 375 granted Oct. 10, 1985 to Albert Schulte Sohne GmbH & Co. discloses a caster wherein a rockable wheel brake is mounted on a pivot member which is rotatably anchored in the upper portion of the wheel frame. As a rule, the pivot member includes a head at one side of the frame, a shank or shaft which extends through the frame, and a retainer (e.g., a nut) engaging the shank or shaft at the other side of the frame. The outwardly extending head and nut detract from the appearance of the assembled caster. The pivotable brake assumes an angular position which is determined exclusively by gravity as soon as the brake is permitted to become disengaged from the peripheral surface of the wheel; this can result in the establishment of rubbing contact between the brake and the wheel, especially if the wheel of the patented caster is caused to roll along an uneven surface. Such rubbing contact can result in the generation of noise and offers at least some resistance to rotation of the wheel at a time when such resistance to rotation is neither desirable nor necessary.
Commonly owned German Pat. No. 38 37 307 granted Nov. 9, 1989 to Albert Schulte Sohne GmbH & Co. discloses a caster wherein the brake is constituted by a pivotably mounted leaf spring which is directly secured to the underside of the upper portion of the wheel frame by a set of screws. The leaf spring is installed in prestressed condition so that it tends to move away from the peripheral surface of the wheel. A drawback of the patented caster is that, as a rule, a leaf spring cannot carry an adjustable brake shoe which would permit compensation for wear upon the brake shoe and/or upon the wheel. In addition, the connection between the leaf spring and the wheel frame (by means of screws) is unreliable if the frame is made of a plastic material. Thus, the screws are likely to become loose in response to repeated flexing of the leaf spring, or the internal threads of the frame are simply destroyed so that the leaf spring becomes completely separated from the frame.